From: Nicholas Nethercote <njn@valgrind.org>
Date: Tue, 30 Nov 2004 11:40:24 +0000 (+0000)
Subject: Get AMD64 slightly further before dying:
X-Git-Tag: svn/VALGRIND_3_0_0~1162
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=244787cc7f00f4d1c73ae5281c3deed13785f5de;p=thirdparty%2Fvalgrind.git

Get AMD64 slightly further before dying:
- implemented VG_(do_syscall)()
- fixed a problem in ume.c with mapping when loading, which was causing
  stage2's memory to be trashed
- fixed stage2.lds substitution so stage2 goes in the right address



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@3156
---

diff --git a/coregrind/amd64-linux/syscall.S b/coregrind/amd64-linux/syscall.S
index af024b4600..2b01fdc41c 100644
--- a/coregrind/amd64-linux/syscall.S
+++ b/coregrind/amd64-linux/syscall.S
@@ -31,11 +31,42 @@
 #include "core_asm.h"
 #include "vki_unistd.h"
 
-# XXX: must reinstate comments also -- see x86-linux/syscall.S
+/*
+	Perform a Linux syscall with the "syscall" instruction.
+	
+	Incoming args (syscall number + up to 6 args) come in 
+	%rdi, %rsi, %rdx, %rcx, %r8, %r9, and the last one on the stack
+	(ie. the C calling convention).
+
+	They are passed to the syscall in the regs
+	%rdi, %rsi, %rdx, %r10, %r8, %r9 (yes, really %r10, not %rcx), ie. the
+	kernel's syscall calling convention.
 
+	%rax holds the syscall number and gets the return value.
+	%rcx and %r11 are clobbered by the syscall;  no matter, they
+	are caller-save (the syscall clobbers no callee-save regs, so
+	we don't have to do any register saving/restoring).
+
+	This has no effect on the virtual machine; the expectation is
+	that the syscall mechanism makes no useful changes to any
+	register except %rax, which is returned.
+*/
 .globl	VG_(do_syscall)
 VG_(do_syscall):
-	ud2
+	# Convert function calling convention --> syscall calling convention
+	movq	%rdi, %rax
+	movq	%rsi, %rdi
+	movq	%rdx, %rsi
+	movq	%rcx, %rdx
+	movq	%r8,  %r10
+	movq	%r9,  %r8
+	movq    8(%rsp), %r9		# last arg from stack
+	syscall
+	ret
+
+
+
+# XXX: must reinstate comments also -- see x86-linux/syscall.S
 
 .globl VG_(clone)
 VG_(clone):
diff --git a/coregrind/amd64/Makefile.am b/coregrind/amd64/Makefile.am
index 2c39310c14..c87e43b4bf 100644
--- a/coregrind/amd64/Makefile.am
+++ b/coregrind/amd64/Makefile.am
@@ -30,4 +30,4 @@ stage2.lds: Makefile
 	$(CC) -Wl,--verbose -nostdlib 2>&1 | sed \
 		-e '1,/^=====\+$$/d' \
 		-e '/^=====\+$$/d' \
-		-e 's/0x00400000/kickstart_base/g' > $@ || rm -f $@
+		-e 's/0x400000/kickstart_base/g' > $@ || rm -f $@
diff --git a/coregrind/ume.c b/coregrind/ume.c
index 00357241d8..14120484f1 100644
--- a/coregrind/ume.c
+++ b/coregrind/ume.c
@@ -225,7 +225,6 @@ ESZ(Addr) mapelf(struct elfinfo *e, ESZ(Addr) base)
       ESZ(Off) off;
       ESZ(Word) filesz;
       ESZ(Word) memsz;
-      ESZ(Word) align;
       unsigned prot = 0;
 
       if (ph->p_type != PT_LOAD)
@@ -235,7 +234,6 @@ ESZ(Addr) mapelf(struct elfinfo *e, ESZ(Addr) base)
       if (ph->p_flags & PF_W) prot |= PROT_WRITE;
       if (ph->p_flags & PF_R) prot |= PROT_READ;
 
-      align   = ph->p_align;
       addr    = ph->p_vaddr+base;
       off     = ph->p_offset;
       filesz  = ph->p_filesz;
@@ -243,21 +241,25 @@ ESZ(Addr) mapelf(struct elfinfo *e, ESZ(Addr) base)
       memsz   = ph->p_memsz;
       brkaddr = addr+memsz;
 
-      res = mmap((char *)ROUNDDN(addr, align),
-                 ROUNDUP(bss, align)-ROUNDDN(addr, align),
-                 prot, MAP_FIXED|MAP_PRIVATE, e->fd, ROUNDDN(off, align));
-      check_mmap(res, (char*)ROUNDDN(addr,align),
-                 ROUNDUP(bss, align)-ROUNDDN(addr, align));
+      // Tom says: In the following, do what the Linux kernel does and only
+      // map the pages that are required instead of rounding everything to
+      // the specified alignment (ph->p_align).  (AMD64 doesn't work if you
+      // use ph->p_align -- part of stage2's memory gets trashed somehow.)
 
-      /* if memsz > filesz, then we need to fill the remainder with zeroed pages */
+      res = mmap((char *)PGROUNDDN(addr), PGROUNDUP(bss)-PGROUNDDN(addr),
+                 prot, MAP_FIXED|MAP_PRIVATE, e->fd, PGROUNDDN(off));
+      check_mmap(res, (char*)PGROUNDDN(addr),
+                 PGROUNDUP(bss)-PGROUNDDN(addr));
+
+      // if memsz > filesz, fill the remainder with zeroed pages
       if (memsz > filesz) {
 	 UInt bytes;
 
-	 bytes = ROUNDUP(brkaddr, align)-ROUNDUP(bss, align);
+	 bytes = PGROUNDUP(brkaddr)-PGROUNDUP(bss);
 	 if (bytes > 0) {
-	    res = mmap((char *)ROUNDUP(bss, align), bytes,
+	    res = mmap((char *)PGROUNDUP(bss), bytes,
 		       prot, MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
-            check_mmap(res, (char*)ROUNDUP(bss,align), bytes);
+            check_mmap(res, (char*)PGROUNDUP(bss), bytes);
          }
 
 	 bytes = bss & (VKI_PAGE_SIZE - 1);